Abstract

We describe a smart-pixel circuit that permits the use of a
GaAs/AlGaAs multiple quantum well diode to be used both as a detector for
data input and a modulator for data output. The module provides the ability to
double the number of inputs or outputs to the array and is well suited to
cascaded optoelectronic system architectures that require bidirectional
communition.

Figures (4)

Schematic diagrams of the dual-function
receiver–transmitter circuit: (a) The same diode or diode pair (for
two-beam receivers) used for both optical input and output. (b) The control
channels Ø and Ø2 are complementary signals. When Ø = 1, the circuit acts as a transmitter; when Ø2 = 1, the
circuit behaves as a receiver. The additional pass gate is used to reset the
receiver–transmitter (when Ø1 = 1) input to the proper
operating potential Vtune between the transmit and receive phases. (c) In the
fabricated circuit, a simple inverter buffer was used as the transmitter, and
a transimpedance amplifier circuit constituted the receiver front end.

Operation of the dual-function circuit as (a) a
receiver at 300 Mbits/s and (b) a transmitter at 300 Mbits/s. The
maximum bit rate of the circuit was measured to be 400 Mbits/s, limited by
the receiver bandwidth.